¨make -e" : Bug or Feature?

[Arnd Kohrs]

Hi,

I am assuming that "make -e" will let all environment variables override
variables in the makefile.  Make seems to be inconsistent in setting
variables:

My makefile: bug2.mk
----SNIP---SNAP---
doit: V = Tomato
doit: F = Apple

doitagain: V = Carrot
F = Cherry

doitagain:
        @echo "V= $V"
        @echo "F= $F"

export V F
doit:   
        $(MAKE) -f bug2.mk -e doitagain
----SNIP---SNAP---

Now I call make with the following output:

> $ make -s -f bug2.mk doit
> V= Carrot
> F= Apple

This is odd since I expected ¨V¨ to be set to ¨Tomato¨ (overridden by
the exported environment variable ¨V¨ of the calling make).  However,
the value of ¨F¨ was set as expected.  I conclude that target specific
variables take precedence over environment variables even if the
sub-make is instructed to give precedence to environment variables by
the ¨-e¨ flag.

Now I can verify hypothesis by issuing the following command:

> $ F=Mango make  -esf bug2.mk doit
> V= Carrot
> F= Apple

And voila ¨F¨ was not overridden by the environment variable ¨F¨.

A last experiment using the command-line:

> $ make -esf bug2.mk doit F=Mango
> V= Carrot
> F= Mango

Hm, this is kind of incoherent with previous observations.  What is the
conceptual difference between command-line variable settings and
environment variable settings?  The command-line seems to be more
powerful for setting variable and may even override target specific
variable of sub-makes:

> $ make  -sf bug2.mk doit V=Bean 
> V= Bean
> F= Apple

I am confused.  I would have expected, that ¨make -e¨ with an
environment variable have the same effect as command-line variable
definitions.   Should ¨-e¨ also override target specific variables?

If yes then there is a severe bug in the code.  If not the documentation
should be clear about this behavior.  If this is undefined territory,
I prefer that the behavior of ¨-e¨ with environment variables is
equivalent to passing a variable on the command-line.

Cheers,
Arnd.
-- 
Arnd Kohrs  -  Institut Eurecom - http://www.eurecom.fr/~kohrs
              
The Active WebMuseum: Your personalized access to art paintings.
 Visit now ->  http://www.eurecom.fr/~kohrs/museum.html